GM9S96 Service Manual
SYSTEM OPERATION
9
The minimum required volume
shall be 50 ft
3
per 1,000/Btu/hour (4.8m
3
/kW).
Where the air
volume shall be determined as follows:
(1) For appliances other than fan-assisted, calculate using
the following equation:
Required Volume
other
> 21 ft
3
I
other
ACH 1000 Btu/hr
(2) For fan-assisted appliances, calculate using the following
equation:
Required Volume
fan
> 15 ft
3
I
fan
ACH 1000 Btu/hr
where:
I
other
= all appliances other than fan-assisted input in Btu
per hour
I
fan
= fan-assisted appliances input in Btu per hour
ACH = air change per hour (percent of volume of space
exchanged per hour, expressed as a decimal)
-
er than 0.60 ACH shall not be used in the equations in
9.3.2.2(1) and 9.3.2.2(2).
Openings used
to connect indoor spaces shall be sized and located in accor-
dance with the following:
(1)*Combining spaces on the same story. Each opening shall
have a minimum free area of 1 in.
2
/1000Btu/hr (2200
mm
2
/kW) of the total input rating of all appliances in the
space but not less than 100 in.
2
(0.60m
2
). One opening
shall commence within 12 in. (300 mm) of the top, and
one opening shall commence within 12 in. (300 mm) of
the bottom, of the enclosure [see Figure A.9.3.2.3(1)].
The minimum dimension of air openings shall be not less
than 3 in. (80 mm).
Furnace
Water
Heater
Opening
Chimney or Gas Vent
Opening
(2) Combining spaces in dierent stories. The volumes of
-
municating spaces where such spaces are connected
minimum free area of 2 in.
2
/1000 Btu/hr (4400 mm
2
/kW)
of total input rating of all appliances.
Outdoor combustion air shall
be provided through opening(s) to the outdoors in accordance
with the methods in 9.3.3.1 or 9.3.3.2. The minimum dimen-
sion of air openings shall not be less than 3 in. (80 mm).
Two permanent
openings, one commencing within 12 in. (300 mm) of the top
and one commencing within 12 in. (300 mm) of the bottom, of
the enclosure shall be provided. The openings shall commu-
nicate directly, or by ducts, with the outdoors or spaces that
freely communicate with the outdoors, as follows:
(1)*Where directly communicating with the outdoors or
where communicating to the outdoors through vertical
ducts, each opening shall have a minimum free area of
1 in.
2
/4000 Btu/hr (550 min
2
/kW) of total input rating of all
appliances in the enclosure. [See Figure A.9.3.3.1(1)(a)
and Figure A.9.3.3.1(1)(b).]
Furnace
Water
Heater
Outlet Air
Chimney or Gas Vent
Inlet Air
Ventilation louvers for
unheated crawl space
Alternate
air inlet
Ventilation louvers
(each end of attic)
Furnace
Water
Heater
Outlet Air
Chimney or Gas Vent
Inlet air duct
[ends 1 ft (300 mm)
above floor]
Ventilation louvers
(each end of attic)